Seems you forgot an awful lot more. How about 51 focus points on the D4 vs. 39 on the DF, D4 has HD video, D4 has much longer battery life, D4 has 2 storage slots, D4 has faster higher shutter speed 1/8000 sec on D4. Add in your mentioned D4 has twice the FPS and is built like a tank, the DF with its tinker toy buttons is a rip off at half the price.

Same here. Low ISO performance is covered by the D800. High ISO the Df. IF one does not require the high FPS or the rugged build of the D4, the Df IS actually half the price of a D4.

I would guess that a large percentage of Df owners are also D800 owners.